There are 1,100 missing people from N.J. How do you find them?

TRENTON -- Billy Jones disappeared right out of his own backyard in Vineland in 1962, a parent's worst nightmare.

The last anybody can recall, the three-year-old boy was playing with his little sister and the family dog, Babycakes, before vanishing into thin air.

"It's amazing how things get blocked in your brain and you can't unlock them," his sister, Jill Jones, who was just two years old at the time, said in a recent interview. "I'd give anything to remember all of it."

There are things from her childhood that she can remember so vividly, like holding Billy's hand. But she can't unlock what happened to him.

Police never got to the bottom of it, either, though they suspect Billy Jones was abducted. His disappearance is one of the oldest active missing persons cases in New Jersey, but it's far from the only one.

There are more than 1,100 long-term missing in New Jersey, according to the State Police, and more than 350 unidentified bodies that could bring closure to families whose loved ones disappeared long ago if only authorities could make a match.

On Saturday, May 20, the State Police is holding its first-ever missing persons event, dubbed Missing in New Jersey, which seeks to bring together the families of the Garden State's long-term missing to commiserate and, just maybe, connect a few dots.

The event is planned for 1 p.m. at the Rutgers University College Avenue Student Center in New Brunswick.

Lt. Louis Andrinopoulos, who runs the State Police missing persons unit, said the event is "a day for them to get together, share their stories and meet other people that are also in the situation they are in."

Authorities are also holding out hope they can crack some cases. At the event, they're looking to draw new evidence including DNA swabs from family members of the long-term missing, medical and dental records and other documents from missing persons cases.

Law enforcement and technical staff will be on hand to collect samples and catalogue evidence. Andrinopoulos said even in older cases, there's always a chance advances in technology can improve the odds of making a match.

"The science has gotten much better, much more beneficial for law enforcement," he said. "The more we can do on a cold case to up the odds to make an identification and reunite someone with a loved one, the better it is."

Jill Jones holds out hope her brother Billy's still alive, but she knows time isn't on her side. Her parents held out hope, too, but they passed away never learning what fate met Billy. Jill Jones worries the same will happen to her.

"If he's not alive, I'd like to put his body at rest," she said. "If he is alive, I'd like to meet him just once."

Here's what investigators know: He wore a blue snow suit with silver buttons and tan high-top sneakers. He had a vaccination scar on the back of his left arm that looked like a giraffe. He'd be 57 by now, if he's still alive.

Losing a child is traumatic no matter the circumstances, but when a child goes missing and never turns up, the tragedy never ends.

Jill Jones said he parent were tortured by the endless what-ifs -- the psychic who claimed Billy had been killed by a family member, the strangers who would call and claim he'd been abducted by aliens.

"I prefer to believe that somebody took him and raised him and he's still alive and healthy," she said. "It's easier that way."

More than 15,000 people are reported missing in New Jersey each year, though most of them quickly turn up. Those cases often start with local police departments, but they frequently turn to the State Police's specialized missing persons unit for help.

Andrinopoulos said one of the most memorable -- and difficult -- cases of his career was the disappearance of 12-year-old Autumn Pasquale, the Gloucester County girl whose body was found in a recycling bin after a frantic, two-day search.

He said his officers are trained to methodically retrace the steps of the missing -- searching homes and neighborhoods top-to-bottom, checking EZ Pass records and tracing cell phones, leaving no stone unturned.

But too often, he said, the job comes down to matching bodies recovered across the state to the missing persons who match their descriptions. In those cases, Andrinopoulos said, time can be an investigator's biggest enemy.

"Fingerprints don't last forever," he said. "Dental may or may not be there. However, there are other scientific things we can rely on."

Andrinopoulos said family reference samples -- DNA taken from multiple family members -- is the top source of positive matches in such cases.

That's why investigators are encouraging family members of the long-term missing to turn out to the Rutgers event on Saturday and provide basic DNA cheek swabs to help them find a match.

State Police are also hoping to coax the families of the missing who have long gone unreported. In some cases, Andrinopoulos said, family members are hesitant to come forward or provide DNA and other evidence because they're afraid of law enforcement.

"We're not worried about legal status," he said. "There's an undocumented community out there that sometimes may fail to report somebody as missing because of the fact that they're afraid of any legal ramifications. We are not concerned with that."

But ultimately, Andrinopoulos said, Saturday's event is less about the missing than those they left behind.

"The day is mainly about the loved ones of those 1,100 families," he said. "We want them to come together, share their stories of hope and community and realize they're not alone in their pain."

Missing in New Jersey will be held on Saturday, May 20, 2017 at the Rutgers University College Avenue Student Center, located at 126 College Avenue in New Brunswick. Click here for details.

S.P. Sullivan may be reached at ssullivan@njadvancemedia.com. Follow him on Twitter. Find NJ.com on Facebook.